Colloidal Stability Window for Carboxylated Cellulose Nanocrystals: Considerations for Handling, Characterization,...

Area of Science:

• Materials Science
• Nanotechnology
• Colloid Chemistry

Background:

• Cellulose nanocrystals (CNCs) production is increasing for sustainable materials.
• Carboxylated CNCs offer an alternative to traditional sulfated CNCs.
• Understanding CNC colloidal stability is crucial for their application.

Purpose of the Study:

• Define the colloidal stability window for carboxylated CNCs (DextraCel).
• Compare stability with sulfated CNCs under varying conditions.
• Provide guidelines for handling CNCs in industrial applications.

Main Methods:

• Phase diagrams were constructed based on pH, ionic strength, surface charge, counterion, and concentration.
• The pKa of carboxylated CNCs was determined.
• Stability was assessed with and without industrially relevant additives.

Main Results:

• Carboxylated CNCs are stable from pH 3 to 11 (0.5-1.5 wt %) without salt.
• Stability is highly sensitive to ionic strength, with agglomeration at 5 mM NaCl.
• Surface charge and counterion significantly influence stability; carboxylated CNCs are more stable in sodium form.

Conclusions:

• Carboxylated CNCs exhibit a specific colloidal stability window influenced by solution conditions.
• Dilution or pH adjustment cannot restore stability outside this window; ultrasonication is effective for redispersion.
• Guidelines for handling carboxylated CNCs are provided to enhance their use in various products.